chore: improve index.d.ts generation

[amk-dev]

Fixes #205, #191

Changes

1. Update the index.d.ts location from index.d.ts to dist/index.d.ts
2. Generate index.d.ts automatically
3. Remove the manually written index.d.ts
4. Add tsup as a dev dep,
   • this tool is used to generate the index.d.ts
   • this can also be used to bundle the library, its build with esbuild under the hood, and has support for @microsoft/api-extractor which i wanted to use previously.
   • not using any api-extractor features, but it can be used if the need arises.
5. Augment global to have expect included in the declaration files
6. Make anthropicKey and mailosaur fields & child fields optional in ShortestConfig, because they can come from env variables

Note: in some previous commits, i can see tsup was used initially for bundling and then removed. that's why i kept it only for generating types. any reason for this ?

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Name	Status	Preview	Comments	Updated (UTC)
shortest	❌ Failed (Inspect)			Jan 2, 2025 1:29am

[slavingia]

Getting an autofix linting error.

[amk-dev]

type error resolved.

is #238 taking precedence over this ? @m2rads

this PR takes care of the global expect also, without needing to update existing tests. also tsup is a dev dependency and does not affect the bundle in anyway.

i did not update the build:js / build:cli commands, but would be tsup would be a good choice there also ?